When you discover a new favorite author, you want to dive in and read all of his or her works — but sometimes, that means a paltry stack of five or six books. And then there are some authors whose output would take years to read. Here are the 11 most prolific science fiction and fantasy authors of all time.

Top image: The Stars are Ours by Andre Norton.

Note: These include authors who have written over 100 novels, or over about 200 short stories TOTAL. We're not including relatively newer authors whose recent output has been prodigious, such as Charles Stross, Seanan McGuire or Elizabeth Bear. Also, feel free to point out anyone we might have missed in the comments.

1) Lionel Fanthorpe

The Reverend Lionel Fanthorpe, an Anglican vicar, wrote for Badger Books during the 1950s and 60s under many pseudonyms, possibly more than 20 different names in total. Due to the sheer number of books under different names, which were sometimes being used by other authors for Badger Books at the same time, there is no complete bibliography. Collectors estimate that Fanthrope wrote over 180 books, 89 which were written during a 3 year period. On average he completed a book every 12 days. To quote from the Fanthorpe fan page:

Badger Books would send Fanthorpe a cover painting, often the more lurid the better (see the Cover Gallery for examples). He would be asked to write a back-cover blurb and suggest several titles for the book to go along with the art. After a title was settled on, he would start writing the novel. A humorous example is The Last Valkyrie. For those of you who don't know, a Valkyrie is a mythological Norse figure who took valiant warriors from the battlefield straight to Valhalla where they would feast and fight forever in paradise. The Last Valkyrie is set mainly in ancient Greece. It concerns Daedelus, his son Icarus and King Minos. Near the end of the book one chapter is devoted to explaining the whole of Norse mythology. It has the feel of a last minute realization of "We need to fill another 20 pages! Oh, and I should bring Valkyries into this somewhere."

Neil Gaiman is frequently quoted as having said, "Do not read too much Lionel Fanthorpe at one go, your brains will turn to guacamole and drip out of your ears."

2) Mercedes Lackey

Mercedes Lackey began publishing in 1987 with her book Arrows of the Queen. Since then she has published 142 books, an average of 5.5 books/year. Some 30 of those books are in in the Valdemar Saga, her best known works. Lackey is still publishing books, with at least two books scheduled to be published in 2014. She has collaborated on eight books, with co-authors including Eric Flint, Dave Freer, James Mallory, Rosemary Edghill, and others.

3) Piers Anthony

Piers Anthony is a renowned science fiction/fantasy author who believes that one of his greatest achievements is having published a book for every letter of the alphabet. He is best known for the the Xanth series. Between 1967-2013, he wrote over 100 books, averaging almost three books a year, and he's still writing and publishing today. The 37th Xanth novel, Esrever Doom, will be out later this month.

4) Walter Gibson

Walter B. Gibson, under the name Maxwell Grant, is credited with writing the pulp adventures of The Shadow during the 1930s and 40s. He wrote 282 of the 325 Shadow novels, often writing up to 10,000 words a day. He wrote on average 24 novels a year — because his contract stated that if he could write more than 24 novels in a year, the publisher would give him more assignments to fill his "slack time." Gibson also wrote for the Biff Brewster series. In addition to his fiction work he was a practicing magician and wrote many books on magic and the occult. He was once featured in an advertisement for Corona typewriters (at left) that claimed he wrote an astounding 1,440,000 words in less than 10 months.

5) Harry Turtledove

Harry Turtledove, best known for his alternate history novels, has written 120 books and is still writing. In the 34 years he has been publishing, Turtledove has averaged 3.5 books/year. He has written under some pseudonyms, including Eric G. Iverson and Mark Gordian, and he has also collaborated with authors such as Richard Dreyfuss, Judith Tarr, S.M. Stirling and Kevin Sandes.

6) Andre Norton

Andre Norton was a prolific fantasy author, best known for the Witch World series. She was the author or co-author of over 250 novels, including 52 books with collaborators. Between her first publication in 1934 and her death in 2005 she published an average of 3.5 novels a year.

7) Isaac Asimov

Isaac Asimov was one of the most successful and influential science fiction writers of all time. He wrote so many books, short stories, and essays that it’s difficult to find an accurate count. Even Asimov himself didn’t believe he had a complete bibliography of his work. By most accounts, he published well over 500 books in 9 of the 10 Dewey Decimal categories. By the end of his life he had published well over 400 pieces of short fiction, including the Foundation series and the Robot series.

8) Brian Aldiss

Brian Aldiss is one of the most influential and prolific British science fiction writers. In addition to being the first president of the British Science Fiction Association, he has written dozens of books and hundreds of short stories. Between 1942 and the present he wrote 65 novels, almost one book every year — but his most impressive output comes from short fiction: he wrote over 370 short stories between 1954 and 2011, about seven stories a year.

9) Wolfgang Hohlbein

This German author has published over 200 novels, and is still writing — but very few of his books have been translated into English. He's the co-author of the Enwor series, about Skar, a member of a traveling martial arts clan called the Sakai. Some of his books also involve retellings of Germanic folklore — and he's also written a number of Indiana Jones novels that were never translated into English.

10) Ray Bradbury

Best known for Fahrenheit 451, Ray Bradbury was actually most prolific with short fiction. Many of his novels were actually pieced together collections of previously published short stories. He also wrote plays, television scripts, essays, poems and short stories. In total he published over 600 short stories in his 72 year career, averaging eight stories per year.

11) R. A. Salvatore

Even R.A. Salvatore himself can’t keep track of how many books he’s written. When asked how many Dark Elf books he’s published he guesses 23 — admitting that he might have forgotten a few. He is best known for the Forgotten Realms novels. Since he published his first novel, The Crystal Shard, in 1988, Salvatore has written well over 100 books. On average he publishes four books per year. He is still publishing today with at least one book scheduled to come out in 2014.

Also noteworthy:

Marion Zimmer Bradley, with dozens of novels including the Darkover series, Michael Moorcock, with 70 novels and 150 short stories, Tanith Lee, with 79 books and 100 short stories, Stephen King, with 94 novels and 185 short stories; C.J. Cherryh, with 70 novels and 83 short stories and novelettes; Arthur C. Clarke with 21 novels and 12 co-authored books — but over 100 books total in various categories; Anne McCaffrey with 52 novels, 28 co-authored novels, and 66 short stories; Philip K. Dick with 44 novels and 121 short stories; and Terry Pratchett with some 55 novels, including 40 Discworld books.